package org.javacore.nio;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.IntBuffer;
import java.nio.channels.FileChannel;

/*
 * Copyright [2015] [Jeff Lee]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @author Jeff Lee
 * @since 2015-10-15 18:38:17 MappedByteBuffer与Old IO的性能比
 */
public class MappedIO {
	private static int numOfInts = 4000000;
	private static int numOfUbuffInts = 200000;

	private abstract static class Tester {
		private String name;

		public Tester(String name) {
			this.name = name;
		}

		// 打印测试时间
		public void runTests() {
			System.out.print(name + ": ");
			try {
				long start = System.nanoTime();
				test();
				double duration = System.nanoTime() - start;
				System.out.format("%.2f\n", duration / 1.0e9);
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		}

		public abstract void test() throws IOException;
	}

	private static Tester[] tests = { new Tester("Stream Write") {
		@Override
		public void test() throws IOException {
			DataOutputStream dos = new DataOutputStream(
					new BufferedOutputStream(new FileOutputStream(new File("data.txt"))));
			for (int i = 0; i < numOfInts; i++)
				dos.writeInt(i);
			dos.close();
		}
	}, new Tester("Mapped Write") {
		@SuppressWarnings("resource")
		@Override
		public void test() throws IOException {
			FileChannel fc = new RandomAccessFile("data.txt", "rw").getChannel();
			IntBuffer ib = fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();
			for (int i = 0; i < numOfInts; i++)
				ib.put(i);
			fc.close();
		}
	}, new Tester("Stream Read") {
		@Override
		public void test() throws IOException {
			DataInputStream dis = new DataInputStream(
					new BufferedInputStream(new FileInputStream(new File("data.txt"))));
			for (int i = 0; i < numOfInts; i++)
				dis.readInt();
			dis.close();
		}
	}, new Tester("Mapped Read") {
		@SuppressWarnings("resource")
		@Override
		public void test() throws IOException {
			FileChannel fc = new FileInputStream(new File("data.txt")).getChannel();
			IntBuffer ib = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size()).asIntBuffer();
			while (ib.hasRemaining())
				ib.get();
			fc.close();
		}
	}, new Tester("Stream Read/Write") {
		@Override
		public void test() throws IOException {
			RandomAccessFile raf = new RandomAccessFile(new File("data.txt"), "rw");
			raf.writeInt(1);
			for (int i = 0; i < numOfUbuffInts; i++) {
				raf.seek(raf.length() - 4);
				raf.writeInt(raf.readInt());
			}
			raf.close();
		}
	}, new Tester("Mapped Read/Write") {
		@SuppressWarnings("resource")
		@Override
		public void test() throws IOException {
			FileChannel fc = new RandomAccessFile(new File("data.txt"), "rw").getChannel();
			IntBuffer ib = fc.map(FileChannel.MapMode.READ_WRITE, 0, fc.size()).asIntBuffer();
			ib.put(0);
			for (int i = 1; i < numOfUbuffInts; i++)
				ib.put(ib.get(i - 1));
			fc.close();
		}
	} };

	public static void main(String[] args) {
		for (Tester tester : tests)
			tester.runTests();
	}
}
